Various electro-optical systems have been developed for reading optical indicia, such as barcodes. A barcode is a coded pattern of graphical indicia comprised of a series of bars and spaces of varying widths, the bars and spaces having differing light reflecting characteristics. The pattern of the bars and spaces encode information. Barcode may be one dimensional (e.g., UPC barcode) or two dimensional (e.g., DataMatrix barcode). Systems that read, that is, image or scan and decode barcodes employing imaging camera systems or laser scanner systems are typically referred to as optical scanners or barcode scanners.
Optical scanners may be portable or stationary. A portable optical scanner is one that is adapted to be held in a user's hand and moved with respect to target indicia, such as a target barcode, to be read that is, imaged or scanned and decoded. Some stationary optical scanners are mounted in a fixed position, for example, relative to a point-of-sales counter. Examples of such point-of-sale optical scanners are further described in U.S. Pat. No. 6,631,845 entitled TWO WINDOW OPTICAL SCANNER that issued Oct. 14, 2003 and U.S. Pat. No. 6,854,655 entitled TWO WINDOW OPTICAL SCANNER that issued Feb. 15, 2005. Both the U.S. Pat. Nos. 6,631,845 and 6,854,655 are incorporated herein by reference in their entireties.
Target objects, such as a product package that includes a target barcode are moved or swiped past one of the one or more transparent windows and thereby pass within a field-of-view of the stationary optical scanners. The optical scanner typically provides an audible and/or visual signal to indicate the target barcode has been successfully imaged or scanned and decoded. Sometimes barcodes are presented, as opposed to swiped. This typically happens when the swiped barcode failed to scan, so the operator tries a second time to scan it. Alternately, presentation is done by inexperience users, such as when the reader is installed in a self check out installation.
A typical example where a stationary optical scanner would be utilized includes a point of sale counter/cash register where customers pay for their purchases. The optical scanner is typically enclosed in a housing that is installed in the counter and normally includes a vertically oriented transparent window and/or a horizontally oriented transparent window, either of which may be used for reading the target barcode affixed to the target object, i.e., the product or product packaging for the product having the target barcode imprinted or affixed to it. The sales person (or customer in the case of self-service check out) sequentially presents each target object's barcode either to the vertically oriented window or the horizontally oriented window, whichever is more convenient given the specific size and shape of the target object and the position of the barcode on the target object.
A stationary optical scanner for reading barcodes typically has a plurality of imaging cameras can be referred to as a multi-camera imaging-based scanner or barcode reader. In a multi-camera imaging reader, each camera system typically is positioned behind one of the plurality of transparent windows such that it has a different field-of-view from every other camera system. While the fields of view may overlap to some degree, the effective or total field-of-view of the reader is increased by adding additional camera systems. Hence, the desirability of multicamera readers as compared to signal camera readers which have a smaller effective field-of-view and require presentation of a target barcode to the reader in a very limited orientation to obtain a successful, decodable image, that is, an image of the target barcode that is decodable.
The camera systems of a multi-camera imaging reader or multi-camera optical scanner may be positioned within the housing and with respect to the transparent windows such that when a target object is presented to the housing for reading the target barcode on the target object, the target object is imaged by the plurality of imaging camera systems, each camera providing a different image of the target object. Further explanation of this concept is discussed in U.S. patent application Ser. No. 11/862,568 filed Sep. 27, 2007 entitled MULTIPLE CAMERA IMAGING BASED BARCODE READER and Ser. No. 12/241,153 filed Sep. 30, 2008 entitled IMAGING DUAL WINDOW SCANNER WITH PRESENTATION SCANNING, which are assigned to the assignee of the present invention and are incorporated herein by reference.